The James Webb Space Telescope: Hubble's Mind-Blowing Successor | Answers With Joe
发布时间 2018-02-05 13:30:01 来源
摘要
The Hubble Telescope opened our perspective of the cosmos and our place in it. But the James Webb Space Telescope may show us the very origins of our universe.
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LINKS LINKS LINKS:
Animation of the JWST launch and deployment:
https://www.youtube.com/watch?v=v6ihVeEoUdo
JWST focusing procedure:
https://www.youtube.com/watch?v=_2zQiWeXTg4
JWST Documentary:
https://www.youtube.com/watch?v=JnpZzPAsz1U
TRANSCRIPT:
So let’s talk about what we’re getting for our $8 billion dollars shall we?
The first thing everybody talks about with the JWST is the mirror. Or I should say mirrors.
The collecting surface is a massive 6.5 meters, or 21.3 feet, as tall as a two story building. The only way to get a mirror that size into space is to fold it up, so the mirror is made out of 18 hexagonal gold-coated beryllium units that fold together to make one surface.
By the way, the mirror on the Hubble - the mirror that gave us an entirely new perspective on our universe by showing us things we didn’t know were there - is 2.4 meters. This DWARFS Hubble.
And unlike Hubble, which could see in the infrared, visible, and ultraviolet wavelengths, JWST’s will focus on the infrared spectrum
The reason is because JWST’s primary mission is to find the furthest and earliest stars and galaxies in the universe. Think of the Hubble deep field on steroids and meth.
And because of the expansion of the universe, the further a star or galaxy is from us, the more redshifted their light will be.
So the furthest galaxies will be redshifted way down into the deep infrared.
The trick with infrared telescopes is in order to see the smallest frequencies, you have to be really cold. Most Infrared telescopes have very short life spans for this reason because they’re cooled with liquid nitrogen or helium. These things are so sensitive that even the heat from the computer on the telescope can mess with the results.
But James Webb cools passively as much as possible through the solar shields. These shields are the size of a tennis court but are thinner than a human hair.
They have to be insanely thin to keep from weighing too much.
One specific star JWST plans to check out is KIC 8462852 - Tabby’s Star, which I just covered about a month ago in a video that will likely be obsolete once JWST takes a look at it.
LUVOIR is a 12-meter telescope that can see in multiple wavelengths, including the visible spectrum, which James Webb can’t do.
It would be used to study galaxy formation and examine the early universe even further than James Webb, but maybe the coolest part is it will have an onboard chronograph that blocks starlight, meaning it’ll be able to find exoplanets visibly without the planet’s star getting in the way.
Perched atop Mauna Kea, the Thirty Meter Telescope’s mirror has a diameter of - you guessed it - 30 meters, with a collection area of 655 square meters, made up of 492 individual segments.
This will have capabilities from ultraviolet, through the visible spectrum and into the mid-infrared field, giving it a wide range of wavelengths to cover.
There are a couple more extremely large telescopes in the works worth mentioning, including the European Extremely Large Telescope with a diameter of nearly 40 meters and the Magellan Telescope, both of which are set to be built in Chile.
But all of this is dwarfed by the Chinese five hundred meter Aperture Spherical Telescope - or FAST.
This is a radio telescope that is twice as large as the Arecibo telescope in Puerto Rico. It got its first light in 2016 and has already discovered a pair of pulsars, though it’s still a ways away from being fully operational.
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